I can't explain it, but I believe you're right.
By my calculations:
Hit points: 600 (24 * 25)
Heavy pivot gun: 145
4 medium guns: 260
Medium pivot gun: 85
I would have responded earlier but I just got back from vacation.
Looking at the tables in the back, the Tuscaloosa is 1240 pts. Going with the info on the table, this is correct. In the table, it doesn't list the ram but does list the shallow draught. What's going on the image is beyond me, but it must just be to show off the form filled out.